The purpose of the proposed research is to determine whether the cellular immune reactions of larvae of Drosophila are activated by hormonal changes that occur during infection, and to identify the chemotactic agent(s) produced that causes the blood cells to leave areas where they are normally found and encapsulate parasites. The study is also concerned with the morphological and physiological changes that occur in the blood cells, as well as the histopathological changes that occur in the neuroendocrine centers of the hosts during infection.